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    Subject[PATCH 5.18 346/879] ALSA: pcm: Check for null pointer of pointer substream before dereferencing it
    Date
    From: Colin Ian King <colin.i.king@gmail.com>

    [ Upstream commit 011b559be832194f992f73d6c0d5485f5925a10b ]

    Pointer substream is being dereferenced on the assignment of pointer card
    before substream is being null checked with the macro PCM_RUNTIME_CHECK.
    Although PCM_RUNTIME_CHECK calls BUG_ON, it still is useful to perform the
    the pointer check before card is assigned.

    Fixes: d4cfb30fce03 ("ALSA: pcm: Set per-card upper limit of PCM buffer allocations")
    Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
    Link: https://lore.kernel.org/r/20220424205945.1372247-1-colin.i.king@gmail.com
    Signed-off-by: Takashi Iwai <tiwai@suse.de>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    sound/core/pcm_memory.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    diff --git a/sound/core/pcm_memory.c b/sound/core/pcm_memory.c
    index 8848d2f3160d..b8296b6eb2c1 100644
    --- a/sound/core/pcm_memory.c
    +++ b/sound/core/pcm_memory.c
    @@ -453,7 +453,6 @@ EXPORT_SYMBOL(snd_pcm_lib_malloc_pages);
    */
    int snd_pcm_lib_free_pages(struct snd_pcm_substream *substream)
    {
    - struct snd_card *card = substream->pcm->card;
    struct snd_pcm_runtime *runtime;

    if (PCM_RUNTIME_CHECK(substream))
    @@ -462,6 +461,8 @@ int snd_pcm_lib_free_pages(struct snd_pcm_substream *substream)
    if (runtime->dma_area == NULL)
    return 0;
    if (runtime->dma_buffer_p != &substream->dma_buffer) {
    + struct snd_card *card = substream->pcm->card;
    +
    /* it's a newly allocated buffer. release it now. */
    do_free_pages(card, runtime->dma_buffer_p);
    kfree(runtime->dma_buffer_p);
    --
    2.35.1


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